<PRE><B>Question 318285</B>
Two cars leave City A at the same time to travel to City B.
One car travels at 72 km/h and other at 78 km/h. If the slower car arrives 20 min
after the faster car, how far apart are City A and City B?
:
Let d = distance from City A, to City B
:
Change 20 min to {{{1/3}}} hr
:
slow car time - fast car time = 20 min
{{{d/72}}} - {{{d/78}}} = {{{1/3}}}
Multiply equation by 5616 (78*72), results
78d - 72d = 1872
:
6d = 5616
:
d = {{{1872/6}}}
d = 312 mi
;
:
Check solution
{{{312/72}}} - {{{312/78}}} = 
{{{13/3}}} - {{{12/3}}} = {{{1/3}}}
</PRE>